Civil Engineering Reference
In-Depth Information
CHAPTER 4
Mixing Water for Concrete
Almost any natural water that is drinkable and has no
pronounced taste or odor can be used as mixing water for
making concrete (Fig. 4-1). However, some waters that are
not fit for drinking may be suitable for use in concrete.
Six typical analyses of city water supplies and seawa-
ter are shown in Table 4-1. These waters approximate the
composition of domestic water supplies for most of the
cities over 20,000 population in the United States and
Canada. Water from any of these sources is suitable for
making concrete. A water source comparable in analysis
to any of the waters in the table is probably satisfactory for
use in concrete (Fig. 4-2).
Water of questionable suitability can be used for
making concrete if mortar cubes (ASTM C 109 or AASHTO
T 106) made with it have 7-day strengths equal to at least
90% of companion specimens made with drinkable or
distilled water. In addition, ASTM C 191 (AASHTO T 131)
tests should be made to ensure that impurities in the
mixing water do not adversely shorten or extend the
setting time of the cement. Acceptable criteria for water to
be used in concrete are given in ASTM C 94 (AASHTO M
157) and AASHTO T 26 (see Tables 4-2 and 4-3).
Fig. 4-1. Water that is safe to drink is safe to use in con-
crete. (44181)
Excessive impurities in mixing water not only may
affect setting time and concrete strength, but also may
cause efflorescence, staining, corrosion of reinforcement,
volume instability, and reduced durability. Therefore,
certain optional limits may be set on chlorides, sulfates,
Table 4-1. Typical Analyses of City Water Supplies and Seawater, parts per million
Analysis No.
Chemicals
1
2
3
4
5
6
Seawater*
Silica (Si
2
)
2.4
0.0
6.5
9.4
22.0
3.0
—
Iron (Fe)
0.1
0.0
0.0
0.2
0.1
0.0
—
Calcium (Ca)
5.8
15.3
29.5
96.0
3.0
1.3
50 to 480
Magnesium (Mg)
1.4
5.5
7.6
27.0
2.4
0.3
260 to 1410
Sodium (Na)
1.7
16.1
2.3
183.0
215.0
1.4
2190 to 12,200
Potassium (K)
0.7
0.0
1.6
18.0
9.8
0.2
70 to 550
Bicarbonate (HC
3
)
14.0
35.8
122.0
334.0
549.0
4.1
—
Sulfate (SO
4
)
9.7
59.9
5.3
121.0
11.0
2.6
580 to 2810
Chloride (Cl)
2.0
3.0
1.4
280.0
22.0
1.0
3960 to 20,000
Nitrate (NO
3
)
0.5
0.0
1.6
0.2
0.5
0.0
—
Total dissolved solids
31.0
250.0
125.0
983.0
564.0
19.0
35,000
* Different seas contain different amounts of dissolved salts.
